Photosensitive medium comprising a furfurylidene,a lower haloalkane,and a homopolymer of polyvinyl chloride as binder

ABSTRACT

NEGATIVE-WORKING COPYING MATERIALS ARE PREPARED BY COATING A PAPER OR FILM SUBSTRATE WITH AN AMINE-FREE FORMULATION COMPRISING A HOMOPOLYMER OF POLYVINYL CHLORIDE, A CYCLIC ACETAL OF FURFURAL, AND A PHOTOGRSENSITIVE LOWER HALOALKANE. IMAGES ARE FORMED ON THE COPY MATERIALS BY EXPOSURE TO ULTRAVIOLET LIGHT AND FIXED BY HEATING.

United States Patent i PHOTOSENSHTIVE MEDIUM COMPRlSlNG A FURFURYLIDENE,A LOWER HALOALKANE, AND A HOMOPOLYMER OF POLYVHNYL CHLORlDE AS BlNDERdward Zarebski, Holyoke, Mass, assignor to Scott Paper (Zompany,Philadelphia, Pa. No Drawing. Filed Feb. 4, 1972, Ser. No. 223,776 Int.Cl. Gillie 1/52 11.8. Ci. 9688 R 6 Claims ABSTRACT OF THE DiSCLOSURENegative-working copying materials are prepared by coating a paper orfilm substrate with an amine-free formulation comprising a homopolymerof polyvinyl chloride, a cyclic acetal of furfural, and a photosensitivelower haloalkane. Images are formed on the copy materials by exposure toultraviolet light and fixed by heat- BACKGROUND OF THE INVENTION Fieldof the invention The present invention relates generally to improved,negative-working, copy materials and to coating compositions useful inthe preparation thereof. More particularly, the invention relates tocopying materials comprising a paper or film substrate having coatedthereon an aminefree layer comprising a homopolyrner of polyvinylchloride, a cyclic acetal of furfural, and a photosensitive lowerhaloalkane. The copying materials are negative-Working and images areformed thereon by exposure to ultraviolet light and fixed by subsequentheating.

Description of the prior art Copying materials, as that term is commonlyused, refers to any one of many products useful in the reproduction ofgraphic originals. On the basis of the type of copy obtained, thesematerials are referred to as either positive-working ornegative-working. With the positiveworking materials, a print which isthe exact duplicate of the original being reproduced is obtained. Withthe negative-working materials, however, the print obtained is theopposite of the original, i.e., the non-image, or clear, areas of theoriginal will appear as the imaged portions of the copy and the imaged,or printed, areas of the original will not appear on the copy.

The most widely used negative-working copying materials are thoseemploying silver halides. These materials, in addition to beingexpensive, generally require complex equipment and lengthy processingoperations for development of the images. Many attempts have been madeto produce negative-working, non-silver halide, copying materials, butnone of those which have been developed and are reported in theliterature have achieved significant commercial success due to a numberof limitations which are inherent in these materials also.

Several negative-working imaging systems have been proposed in which aphotosensitive haloalkane, such as iodoform, which is known to releasehydrogen iodide (HI) when exposed to light, is combined with a compoundcontaining a furan ring. See, for example, US. Pats. 1,587,269;1,587,272; 1,587,273 and 1,587,274 issued to Beebe and US. Pats.3,394,391 issued to Wiswell, 3,394,- 392 issued to Mattor and 3,394,394and 3,394,395 both of which were issued to Mattor et al. Limitations ofthese systems which have restricted their use include, for example, (a)the presence of impurities in the coatings resulting in discoloration ofthe non-image areas of the copies produced, (b) the high temperaturesrequired to fix the images resulting in a softening and distortion of3,745,912 Patented July 10, 1973 the imaged material, (0) the use ofamines which have a tendency to migrate away from the photosensitivelayer during storage of the materials, (d) poor shelf life of the coatedmaterials, (e) discoloration of the imaged materials and (f) the use ofbinder resins which require the use of toxic solvents or prevent thecomplete release of the photosensitive lower haloalkane from thenon-image areas of the print during the fixing step. If the haloalkaneis not removed from the non-image areas of the print, these areas willdiscolor upon repeated exposure to light.

It is also known that a photosensitive resin, such as a vinyl chloridepolymer, a vinyl chloride-vinyl acetate copolymer or a vinylidenechloride polymer, will produce visible images upon exposure to actiniclight. See, for example, U.S. Pats. 2,712,996; 2,754,210; 2,772,158 and2,772,159 issued to Elliott. However, because these resins do degradewhen exposed to heat and/or light, the stability of both the unimagedand imaged materials is poor.

SUMMARY OF THE INVENTION DESCRIPTION OF THE PREFERRED EMBODIMENTSAccording to the present invention, improved, negativeworlring, copyingmaterials are prepared by coating a paper or film substrate with anamine-free formulation comprising a homopolymer of polyvinyl chloride, acyclic acetal of furfural and a photosensitive lower haloalkane.

The substrate in the present invention may be either paper or film.Preferred bases include paper, cellulose acetate films, and polyesterfilms which have been treated with a suitable subbing layer including,for example, cellulose acetate butyrate.

The formulation is prepared by dissolving the components in an organicsolvent such as, for example, acetone, toluene, methyl ethyl ketone, andtetrahydrofuran.

Polyvinyl chloride homopolymers have been found to be especially usefulas binder resins in the copying materials of the present invention.These polymers are soluble in conventional, non-toxic solvents andresult in copy materials which do not soften when heated, remain clearand colorless in the non-image areas during storage and during the lightexposure and heat curing steps, and allow iodoform, or other haloalkane,to pass from the copy material during the heat fixing step.

A cyclic acetal of furfural is also required. While some of the priorart systems have employed other types of compounds containing a furanring, it has been found that only the cyclic acetals of furfural can beemployed in the copy materials of this invention. Other compounds suchas those containing basic nitrogen groups result in problems such aspoor image density; discolored background or non-image areas, and pooraging characteristics of the coated, unimaged material. Cyclic acetalsuseful in carrying out the present invention include, but are notlimited to, the following:

2-(2-fury1) -1.3 dioxane CH3 E 0... o

2-(2-furyl)-4,6 dimethyl 1,3 dioxane Cyclic acetals of the type usefulin the present invention can be prepared by the following generalprocedure:

0.50 mole of the diol and 1.0 gram of para-toluenesulfonic acid aredissolved in 150 cc. of tetrahydrofuran and the resulting solution isplaced in a 4 necked 1 liter flask equipped with stirring apparatus, anaddition funnel, a Dean-Stark trap and a thermometer. 150 cc. of pentaneare added and the reaction mixture is heated to reflux and 0.50 mole offurfural (1.0 mole when the diol is pentaerythritol) are added dropwisethrough the addition funnel. After the addition of the furfural iscomplete, the reaction mixture is refluxed until no more water isevolved. The reaction mixture is then neutralized with an aqueoussolution of sodium carbonate and the resulting phases are separated. Theupper, organic phase containing the product is first extracted with warmwater to remove any unreacted diol or furfural and the solvent is thenremoved on a flash evaporator. Solid products are purified byrecrystallization from methyl alcohol and liquid products by fractionaldistillation at reduced pressure.

Several of the compounds specifically enumerated above had the followingphysical properties:

Melting point 0.)

Compound Physical state (or boiling point) White crystals- 161-162.

Colorless liquid 61-63 at 0.5 mm

hits crystals 7. Colorless crystals... 24-26 (boiling point 81 at VWhite crystals 2446.

ing Copying Material filed concurrently herewith by William F. Lonczak.

The coating solution is applied to the substrate by conventionalmethods. These are well known in the art and include, for example,bead-coating, reverse roll, betweenthe-roll coating, and spray coating.

Negative-working copying materials prepared in accordance with thepresent invention can be imaged by exposing, beneath a partially opaquemaster, to ultraviolet light in the range of from about 3000 angstromsto about 5000 angstroms. It is especially preferred to employ a lightsource having an output in the range of from about 3300 angstroms toabout 4500 angstroms. The light exposure results in the formation of animage in the light-struck areas of the copy material-i.e., those areascorresponding to the non-image areas of the master. After exposure theprint is fixed by heating. It is especially preferred to heat the copymaterial to a temperature of from about 140 C. to about 160 C. forapproximately two minutes. The effect of the heating is to remove thephotosensitive lower haloalkane from the background, or non-image areasof the print and to develop, or fix, the image formed upon exposure tolight.

In order to describe the present invention so that it may be moreclearly understood, the following examples are set forth. These examplesare set forth primarily for the purpose of illustration, and anyspecific enumeration of detail contained therein should not beinterpreted as a limitation on the concept of this invention.

EXAMPLE I A coating formulation was prepared comprising Methyl ethylketone cc 100 Opalon 600a polyvinyl chloride homopolymer available fromMonsanto Company, St. Louis,

MO. gms 10.0 Iodoform m 1.0 Difurfurylidene pentaerythritol gm 1.0

EXAMPLE II A coating formulation was prepared comprising Percent Methylethyl ketone 76.49

GAP 2a polyvinyl chloride homopolymer available from Great AmericanPlastics, Inc., Fitchburg, Mass. 14.32 OK412a silica available fromDeGussa 4.87 Difurfurylidene pentaerythritol 2.16

and

Iodoform 2.16

The formulation was reverse roll coated on a Crane rag 14 pound paperbase and dried. The material was exposed, beneath a partially opaquemaster, to ultraviolet light in a Super Ozamatic operating at 10 feetper minute. The result was an image in the light-struck areas i.e.,those areas corresponding to the clear or non-image areas of theoriginal. The image was fixed by heating the exposed material to atemperature of about C. for about two minutes.

The print had a density of about 3.0 when measured in a photoelectricdensitometer calibrated for visual density according to the ASAspecification for reflectance density, PH2..17-l958.

By comparison a material prepared from a formulation utilizingpolyphenylene oxide as the resin resulted in a brownish print on ayellow background.

EXAMPLE III A coating formulation was prepared, as in Example I], andcoated onto a polyester base which had been treated with a suitablebonding layer. The coated material was then dried, exposed and fixed asin Example 11. The resulting black image had a density of about 2.2 whenmeasured as in Example 1.

EXAMPLE IV The formulation was reverse roll coated on Crane 100% rag, 14pound, paper base and dried. The material was exposed and fixed, as inExample II, resulting in a black image on a clear background. The imageareas had a maximum density of 3.10 when measured as in Example 11.

EXAMPLE V A coating formulation was prepared comprising Percent Methylethyl ketone 76.49 GAPS52 14.32

OK412 4.87 2-(2-furyl)-4-methyl-l,3-dioxane 2.34 Iodoform 2.16

The formulation was reverse roll coated on Crane rag, 14 pound, paperbase and dried. The material was exposed and fixed, as in Example II,resulting in a black image on a clear background. The print had amaximum density of 3.10 when measured as in Example II.

What is claimed is:

1. In an amine-free photosensitive coating composition comprising acyclic acetal of furfural, a photosensitive lower haloalkane and abinder resin, the improvement which comprises utilizing a homopolyrnerof polyvinyl chloride as the binder resin.

2. A coating composition as claimed in claim 1, in which the cyclicacetal of furfural is difurfurylidene pentaerythritol.

3. A coating composition, as claimed in claim 1, in which thephotosensitive lower haloalkane is iodoform.

4. In a negative-working copy material comprising a paper or filmsubstrate having coated on one surface thereof an amine-free layercomprising a cyclic acetal of furfural, a photosensitive lowerhaloalkane and a binder resin, the improvement which comprises utilizinga homopolymer of polyvinyl chloride as the binder resin.

5. A copy material, as claimed in claim 4, in which the cyclic acetal offurfural is difurfurylidene pentaerythritol.

6. A copy material, as claimed in claim 4, in which the photosensitivelower haloalkane is iodoform.

References (lifted UNITED STATES PATENTS 7/1968 Mattor et a1 96-90 R7/1968 MattOr 9690R U.S. Cl. X.R.

